The first half of 2012 saw 35,700 cases of malaria and 28 deaths, according to government statistics.

PHNOM PENH - Health officials say they are making headway in their fight against malaria in Cambodia, but they are struggling against drug-resistant strains of the disease, which is spreading in the northwest and is particularly troubling at major migrant crossings like Pailin.

Drug-resistant malaria is particularly prevalent along the Thai-Cambodian border, where resistance is spread by migrant workers passing between the two countries, said Kheang Soy Ty, regional director for University Research, an NGO that fights drug-resistant malaria in sub-Mekong countries.

The first half of 2012 saw 35,700 cases of malaria and 28 deaths, according to government statistics, a slight decrease from the year before. But there are no statistics yet on the number of drug-resistant cases.

Char Meng Chuor, director of the government’s National Malaria Center, said about 17 percent of all cases in the border area of Pailin were drug resistant in 2011, up from 10 percent there the year before. The drug-resistant disease has also spread to parts of Pursat and Preah Vihear provinces, he said.

Drug resistance occurs when a patient infected with the Plasmodium falciparum parasite takes an incomplete or incorrect course of anti-malarial drugs. This allows the parasite to evolve resistance to that medicine, so malaria patients must take the proper drugs under the supervision of a doctor, Meng Chour said.

Drug-resistant malaria is currently more severe in Cambodia than anywhere else in the world, said Steven Bjorge, leader for the World Health Organization’s malaria team in Cambodia. There is no agreed-on reason why, he said, but drug-resistant malaria first evolved there in the 1950s and 1960s.

“Since than every new drug seems to first become resistant in Cambodia or on the Thai-Cambodian border before anywhere else in the world,” he said.

However, he said, the number of cases continues to drop, and with proper malaria control, even the numbers of drug-resistant cases should fall.

“It is not a hopeless situation,” he said. “I am actually hopeful about the future because we are having a lot of success in Cambodia, despite the headlines saying that drug resistance is growing. The main message is that malaria is dropping in Cambodia, and the few cases that remain are the drug-resistant cases.”

The WHO has been changing standard drug treatments to stay ahead of the parasite. Two months ago, it started using a drug called Malarone in Pailin, in the hopes of seeing a decrease.

In a normal case of malaria, a course of drug treatment can eliminate the parasite from the patient’s blood within three days. But in drug-resistant cases, this is not enough to clear the parasite. With these patients, it can take anywhere from five to 28 days to flush out the malaria parasite.

Kheang Soy Ty of University Research said migrant workers are of greatest concern for stopping the spread of the drug-resistant disease. Migrant workers do not have immunities to malaria and carry stronger versions of the disease greater distances. They don’t understand prevention and aren’t as likely to have bed nets, a major protectant. They also don’t know where they can be treated once they get it.

“So if they are infected with the drug-resistant malaria, they become an agent that spreads the resistant malaria faster,” he said.

University Research is trying to ensure migrant workers are given bed nets before they move through malaria-prone areas, he said. Meanwhile, it is training local people to provide malaria treatment.

Uth Sophal, Pailin field-officer for the Malaria Consortium, another health NGO, said the problem is greatest in border towns with a lot of traffic. Here, patients might buy the wrong drugs without seeing a doctor, or misuse treatment in other ways.

“Migrant people move from one province to another, so when they come to Pailin, which already has resistant malaria, when the mosquitoes bite those people, they will get that parasite and pass it from one province to another province, from one country to another,” he said.

The Malaria Consortium has created a network of volunteers at Pailin’s border crossing to check and evaluate migrant workers and treat them if they have malaria.

“When Cambodians cross the border, we measure their temperature,” he said. “If they have any kind of illness, we have to immediately treat them.”

Meng Chuor too said Pailin is the key to stopping the spread of the drug-resistant disease. And the stakes are high.

“Don’t be confused, the resistance is not just one person’s issue,” he said. “Malaria drug resistance is a problem for the whole community…. If mosquitos are imported to other countries, it will go to other countries…. This is a concern of the world about Cambodia now.”